Ab initio Structure Determination of Barium Periodate, Ba 5 I 2 O 12 , from Powder XRD Data

The compound Ba 5 I 2 O 12 was synthesized by heating a precipitate of dissolved Ba(OH) 2 · 8H 2 O and H 5 IO 6 . Rb 2 O was added to increase the crystallite size. The crystal structure was determined from conventional laboratory X‐ray diffraction data by using a real‐space structure solution approach followed by a Rietveld refinement. No constraints on positions were used. The structure analysis gave an orthorhombic symmetry with a = 19.7474(2) Å, b = 5.9006(1) Å and c = 10.5773(1) Å. The final R Bragg value in space group Pnma (62) was 1.0 %. The structure can be described by layers of a metal and iodine arrangement forming almost pentagonal holes. Raman measurements were correlated with the two IO 6 octahedra. Two further barium periodate patterns were observed and indexed.